On the basis of preliminary data and techniques that were validated for the primate fetus, we propose to investigate the physiological actions of steroids during sexual development in rhesus macaques. We will determine the existence of a negative feedback loop between gonadal steroids and the fetal nervous system and (or) pituitary gland that controls luteinizing hormone (LH) secretion. We hope to document developmental differences between the sexes and provide firm evidence for or against the hypothesis that testosterone of fetal origin triggers the release of pituitary LH early in gestation in males. We will describe localization and levels of activity with time of gestation of several key steroid-metabolizing enzymes. Activities of the reductases, aromatases, and 17-hydroxysteroid dehydrogenases are probably important to the progressive changes that produce a "normal" sexually differentiated primate fetus, but their activities throughout gestation are not well defined. Utilizing the fact that the fetal testes do not have late germinal elements, we will test the hypothesis that the cellular components of these stages produce a substance that interferes with steroid-regulated feedback in pituitary gonadotropins in primates. Finally, we propose some developmental work on the relationship of certain pituitary cell types to certain steroid-metabolizing enzymes and to develop antisera for dehydroepiandrosterone and 5-androstene-3 beta, 17 beta-diol as an investment in future research in the biological actions of these steroids in primate fetal development.